Tumor suppressors in lymphocytes The genes that are necessary for normal, controlled cell growth are called tumor suppressor genes, and inactivation of these genes can lead to tumor formation. The majority of known tumor suppressors were located by the genetic mapping of organisms with an inherited predisposition for cancer. However, familial predisposition to cancer is responsible for only approximately 10% of human cancers and identificationof tumor suppressors involved in non-familial cancers has been slower. The goal of this proposal is to define the set of tumor suppressors that when deleted contributeto the formation of lymphocytetumors in mice; and their interactions with protooncogenes, as completely as possible. This will be attempted by retroviral insertionalmutagenesis, combined with chemical mutagenesis, to inactivate both alleles in cells of a given mouse. The offspring of chemically mutagenized male mice are subjected to insertional mutagenesis by retrovirus that induces tumors of lymphocyte origin. The viral genome disrupts potential suppressor genes, leading to their inactivation, and at the same time creates a marker for identifying the insertion loci. The tagged cancer genes will be cloned and sequenced by a high throughput PCR based technique. Subsequently, a subset of them will be further characterized and the nature of their cooperation with other oncogenes (co-mutations) will be determined.